/**
 * 238. 除自身以外数组的乘积
 * https://leetcode.cn/problems/product-of-array-except-self/description/
 */
class Solution {
    public int[] productExceptSelf(int[] nums) {
        //1、预处理数组，构造前缀积数组
        int n = nums.length;
        int[] f = new int[n];
        int[] g = new int[n];
        f[0] = g[n - 1] = 1;
        
        for(int i = 1; i < n; i++) {
            f[i] = f[i - 1] * nums[i - 1];
        }
        for(int i = n - 2; i >= 0; i--) {
            g[i] = g[i + 1] * nums[i + 1];
        }
        //2、使用前缀积数组
        int[] ret = new int[n];
        for(int i = 0; i < n; i++) {
            ret[i] = f[i] * g[i];
        }
        return ret;
    }
}